1. Field
The disclosure relates to a method, system, and program for failover and load balancing.
2. Description of the Related Art
An I_T nexus is a pairing of an initiator device and a target device. The devices that request input/output (I/O) operations are referred to as initiators and the devices that perform these operations are referred to as targets. For example, a host computer may be an initiator, and a storage device may be a target. The target may include one or more separate storage devices.
A Host Bus Adapter (HBA) is a hardware device that “connects” the operating system and a Small Computer System Interface (SCSI) bus. The HBA manages the transfer of data between the host computer and the communication path. HBA teaming refers to grouping together several HBAs to form a “team,” where each HBA in a team is connected and may route data to a particular target. HBA teams may be built on an Internet Small Computer System Interface (iSCSI) (IETF RFC 3347, published February 2003) portal group concept. iSCSI has been defined as a standard by IETF February 2003. A portal group concept may be described as a collection of Network Portals within an iSCSI Network Entity that collectively support the capability of coordinating a session with connections spanning these portals.
HBA teaming may be used with Small Computer System Interface (SCSI) (American National Standards Institute (ANSI) SCSI Controller Commands-2 (SCC-2) NCITS.318:1998) initiators running Windows® 2000, Windows® XP, or Windows® .NET operating systems. The connection recovery strategy of an I_T nexus may be based on multiple Transmission Control Protocol (TCP) connections (Internet Engineering Task Force (IETF) Request for Comments (RFC) 793, published September 1981). That is, packets from iSCSI initiators running on Windows® operating systems are transmitted and/or received through multiple connections between an initiator and a target. If multiple connections to the same target are established within one HBA, then a miniport driver may handle failover (i.e., when one connection fails, routing packets to another connection) and load balancing (i.e., balancing the load among the HBA connections). However, there is a need in the art for failover and load balancing across several HBAs, each of which may have one or more connections to the same target.